Blood Collection Tube Color Guide: Vacutainer Tube Colors & Additives
Meta description: Learn what each blood collection tube color means, which additives are inside, what tests each tube is used for, and the correct order of draw.
Walk into any phlebotomy station or lab and you'll see a rainbow of tube tops: red, gold, light blue, green, lavender, gray, and more. The colors aren't decorative. Each one tells you what additive is inside the tube, and that additive determines which tests can be run on the sample.
Choosing the wrong tube, or filling tubes in the wrong sequence, can produce inaccurate results or force a recollection. This guide covers what each tube color means, the additives behind them, and why order of draw matters.
Why Tube Colors and Additives Matter
Blood tests fall into three main categories, and each needs a different sample type:
- Serum is the liquid portion after blood has clotted. It's used for many chemistry, serology, and immunology tests.
- Plasma is the liquid portion of blood that has been prevented from clotting with an anticoagulant.
- Whole blood is used for tests that need intact cells, such as a complete blood count (CBC).
The additive in each tube (clot activator, anticoagulant, preservative, or gel separator) prepares the sample for its intended test. The cap color is a quick visual cue for which additive is inside.
A note on color standards: Cap colors are broadly consistent across the industry, but not universal. Manufacturers such as BD (the maker of Vacutainer®), Greiner Bio-One, Sarstedt, and Terumo may use slightly different colors or designations for certain tubes. "Vacutainer" is a BD brand name, but many people use it generically for vacuum blood collection tubes. Always confirm with your manufacturer's documentation and your laboratory's test directory.
Quick Reference Chart
| Tube Color | Additive | Sample Type | Common Uses |
|---|---|---|---|
| Yellow (SPS) | Sodium polyanethol sulfonate | Whole blood | Blood cultures |
| Light Blue | Sodium citrate | Plasma | PT/INR, aPTT, fibrinogen, D-dimer, coagulation studies |
| Red | None (glass) or clot activator (plastic) | Serum | Chemistry, serology, immunology, blood bank (glass) |
| Gold / Tiger Top (SST) | Clot activator and gel separator | Serum | Routine chemistry, hormones, lipids, serology |
| Light Green (PST) | Lithium heparin and gel separator | Plasma | Plasma chemistry panels |
| Green | Sodium or lithium heparin | Plasma | STAT chemistries, ammonia, some cytogenetics |
| Lavender | EDTA (K2 or K3) | Whole blood | CBC, HbA1c, molecular tests |
| Pink | K2 EDTA | Whole blood | Blood bank: type and screen, crossmatch |
| Gray | Sodium fluoride and potassium oxalate | Plasma | Glucose, lactate, blood alcohol |
| Royal Blue | None, EDTA, or heparin (varies) | Serum, plasma, or whole blood | Trace elements, toxicology, nutritional studies |
| Tan | K2 EDTA | Whole blood | Lead testing |
| Black | Buffered sodium citrate | Whole blood | Erythrocyte sedimentation rate (ESR) |
| Orange | Thrombin | Serum | Rapid serum tests when fast clotting is needed |
Tube-by-Tube Breakdown
Yellow: Blood Cultures (SPS)
Yellow-top tubes and culture bottles contain sodium polyanethol sulfonate (SPS), which prevents clotting and helps neutralize substances that can inhibit bacterial growth. Culture collection requires strict aseptic technique because any contamination can cause false positives. A different yellow tube containing acid citrate dextrose (ACD) is used for DNA studies, HLA typing, and some specialty testing.
Light Blue: Sodium Citrate
Light blue tubes contain liquid sodium citrate, which prevents clotting by binding calcium. The blood-to-additive ratio is critical (typically 9:1), so these tubes must be filled to the indicated fill line. An underfilled tube can skew coagulation results.
Red: Serum Tubes
Red-top tubes come in two forms. Glass tubes contain no additive and allow blood to clot naturally. Plastic red tubes are coated with a clot activator (typically silica) to speed clotting. They're commonly used for chemistry, serology, and blood bank testing, depending on your lab's requirements.
Gold and Tiger Top: Serum Separator Tubes (SST)
These tubes contain a clot activator plus a gel that forms a barrier between the serum and cells during centrifugation. That makes it easy to pour off or directly analyze clean serum. They're a workhorse for routine chemistry, lipid panels, hormones, and many serology tests. Blood should clot fully (usually about 30 minutes) before centrifuging.
Green: Heparin Tubes
Green-top tubes contain sodium heparin or lithium heparin, which prevents clotting by inhibiting thrombin. Light green tubes (PST) also contain a gel separator for plasma. Because the additive can interfere with certain tests, sodium heparin tubes aren't suitable for sodium measurement, and lithium heparin tubes aren't suitable for lithium levels.
Lavender and Pink: EDTA Tubes
EDTA prevents clotting by binding calcium and preserves cell shape well, which makes it the standard for hematology. Lavender tubes are used for CBCs, HbA1c, and many molecular tests. Pink tubes contain K2 EDTA and are typically reserved for blood bank testing, where labeling and traceability requirements are especially strict.
Gray: Glycolytic Inhibitor
Gray tubes contain sodium fluoride, which blocks glycolysis (the breakdown of glucose by blood cells), and potassium oxalate, which acts as an anticoagulant. This preserves glucose levels in the sample, making gray tubes the right choice for glucose tolerance tests, lactate, and blood alcohol testing.
Royal Blue, Tan, and Other Specialty Tubes
Trace element tubes are manufactured to be very low in metal contamination. Royal blue tubes are used for testing such as zinc, copper, and other trace metals, and tan tubes are used for lead testing. Black tubes are used for ESR, and orange tubes contain thrombin for rapid serum results. Check your lab's directory, since specialty tube requirements vary.
Order of Draw: Why Sequence Matters
When multiple tubes are collected in one venipuncture, the order in which they're filled matters. Additives can carry over from one tube to the next through the needle, contaminating the following tubes and skewing results. For example, EDTA carryover can falsely elevate potassium and lower calcium.
A commonly used order of draw, based on CLSI guidelines, is:
- Blood culture tubes/bottles (yellow SPS)
- Light blue (sodium citrate)
- Red or gold/tiger top (serum tubes, with or without gel)
- Green (heparin)
- Lavender/pink (EDTA)
- Gray (sodium fluoride/potassium oxalate)
Some facilities use slightly different sequences or handle specialty tubes differently, so follow your institution's protocol.
Best Practices for Collection
- Check expiration dates. Vacuum loss and additive degradation in expired tubes can cause improper fills and unreliable results.
- Fill tubes to the proper level. This is especially important for light blue tubes and any tube with a liquid additive.
- Invert tubes gently the number of times the manufacturer recommends. Under-mixing can cause clotting or micro-clots in anticoagulant tubes, while vigorous shaking can cause hemolysis.
- Label immediately at the bedside with patient identifiers, date, time, and collector information.
- Store tubes properly. Keep them at the recommended temperature, away from direct sunlight and moisture.
- Never pour blood between tubes. Transferring blood from one tube to another risks additive contamination and can render the sample unusable.
Common Questions
Can I use a different tube if I run out of the one I need?
Substituting tubes is generally not recommended, because the additive determines whether the test is valid. Confirm with your laboratory first.
Why do some tubes have gel in them?
The gel forms a stable barrier between the cells and the serum or plasma during centrifugation, keeping the sample cleaner and more stable during storage and transport.
Are tube colors the same worldwide?
Mostly, but not always. Standards like ISO 6710 guide tube color coding, but manufacturers and regions can vary. When in doubt, read the label on the tube itself.
Final Thoughts
Understanding tube colors and additives helps ensure quality specimens, accurate results, and fewer recollections, which is better for patients and laboratory teams alike. Keep a color guide handy, follow your facility's order of draw, and when in doubt, check with your lab.
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This article is for educational purposes only and does not replace your facility's protocols, manufacturer instructions, or professional information.
